Interrogating the Osteogenic Potential of Implant Surfaces In Vitro: A Review of Current Assays.

The success of implantable devices relies heavily on their interaction with the host cells facilitating the osseointegration process. However, with so many new surface modifications, with subtly varying design parameters, in vitro assays can, with proper interpretation, provide valuable information for understanding cellular behavior. This review brings together pertinent in vitro experimental protocols available to researchers and discusses them in relationship to the development of the osteoblast phenotype during bone repair. Consideration is also paid to the influence of endothelial and macrophage cells that can substantially change osteogenic cell activity and thus can provide added value for predicting the osseointegration potential in vivo. Due to the diverse and heterogeneous nature of cell types available for culture use, this review concludes that there is no "gold standard" series of assays. Rather, we present guidance in the experimental design of in vitro assays to better identify those surfaces with promising osteogenic potential. Impact statement Titanium implants are already widely used in orthopedics and dentistry, yet, intensive research continues with the aim of modifying and functionalizing implant surfaces to invoke a stronger bone response and to meet current clinical challenges around improving longevity, decreasing morbidity, widening access, and clinical application. A very large number of surface modifications have been studied and the potential for new designs appears to be limitless as new technology grows. This review provides guidance for in vitro assays available to test these technologies, providing a cost-effective means for acquiring robust and physiologically relevant data, before in vivo examination.

Liposomes loaded with transforming growth factor ß1 promote odontogenic differentiation of dental pulp stem cells.

OBJECTIVES: This study investigated whether novel liposome formulations loaded with transforming growth factor ß1 (TGF-ß1) could promote the odontogenic differentiation of human dental pulp stem cells (hDPSCs) for dentine-pulp regeneration. METHODS: 0-100 ng/mL of liposomal TGF-ß1 was prepared using the thin-film hydration method. Release of TGF-ß1 from the liposomes was quantified by an enzyme-linked immunosorbent assay (ELISA). The hDPSCs were treated with different concentrations of liposomal TGF-ß1 and cell viability was tested using an MTT assay. "Osteodentine" differentiation capacity was assessed by RT-qPCR, ELISA and Alizarin red S staining. RESULTS: The ELISA results showed that liposomal TGF-ß1 achieved a controlled and prolonged release over time. The MTT results demonstrated that the liposomes (100 µg/mL) were not cytotoxic to the cells. Liposomal TGF-ß1 up-regulated the expression of "osteodentine" markers, RUNX-2, DMP-1 and DSPP, in hDPSCs after 7 days of treatment and resulted in the accumulation of mineralised nodules. CONCLUSION: This study indicated that liposomes are an effective carrier for delivering TGF-ß1 over time. Liposomal TGF-ß1 promoted dentinogenesis and increased mineralisation in hDPSCs. This highlights the potential of liposomal TGF-ß1 for future use in dentine-pulp regeneration. CLINICAL SIGNIFICANCE: Liposomal TGF-ß1 may be used as a synergist for promoting dentine-pulp regeneration of immature permanent teeth or as a pulp capping agent for inducing reparative dentine formation.